Call diversion system

ABSTRACT

An interface ( 52 ) is provided between a satellite telephone system ( 4 ) and a cellular telephone system ( 5 ) for allowing calls to a user&#39;s cellular telephone to be diverted to a satellite telephone ( 25 ) when the user is unable to use his cellular telephone, for example when on board an aeroplane ( 2 ) fitted with a satellite telephone system ( 20 ). The user inserts a card (which may be the SIM of his mobile phone, or a card compatible with existing satellite telephone equipment) into a suitable reader in the satellite telephone ( 20 ), which causes the satellite ground station&#39;s card verification system ( 42 ) to connect to a host cellular network ( 50 ). The host cellular network has an interface unit ( 52 ) which emulates the operation of a normal base station, so that the host cellular system ( 50 ) acts as if the mobile user&#39;s terminal is roaming on the host network, but is currently “busy”. The interface ( 52 ) also resets the user&#39;s existing call diversion instructions so that when the host cellular system ( 5 ) receives a busy tone frome the base station emulator ( 52 ), it routes calls to the directory number of the terminal ( 20 ).

This invention relates to mobile telephony, and in particular to systemsfor use on board vehicles.

There has been considerable activity in recent years in proposals toallow the use of mobile telephones in environments where conventionalcellular telephony base stations cannot provide coverage, in particularon board ships and aircraft. These vehicles frequently travel beyond therange of land-based cellular base stations, which typically have a rangeof the order of 1 to 10 km.

There are a number of special difficulties to be addressed if a standardcellular telephone is to be used in an aircraft. Firstly, many cellularbase stations have antennas arranged for maximum gain in the horizontalplane, so an airborne cellular telephone may not be able to obtain asignal from any base station, even when flying over land served by acellular base station network. Even if the radio range of the basestations does extend as high as the normal flying height of aircraft,there are further problems. Frequency re-use patterns, which allowseveral base stations to use the same radio frequencies withoutinterference, are designed on the assumption that a mobile unit servedby one base station is not able to exchange radio signals with otherbase stations using the same frequency. This assumption ceases to bevalid if a mobile unit is several thousand meters above the ground,since it may be in line-of-sight of a large number of base stationssimultaneously. Moreover, although reliable handover of a mobile unitcan be achieved from moving vehicles travelling at speeds of up to 200km/h, a typical passenger aircraft travels at speeds approaching 1000km/h. Airlines also impose restrictions on the use of powerful radiosignals on board, as a precaution against possible interference with theaircraft's electronic systems.

For truly global coverage, satellite telephones are available. However,these are expensive and much heavier than a cellular telephone. Bothcellular telephones and satellite telephones also suffer from thescreening effect of being inside a metal hulled vehicle. As withcellular telephones, the unrestricted use of a portable satellitetelephone within an aircraft may be prohibited.

A user without his own satellite telephone may use special facilitiesprovided on board, such as the service provided to several airlines bythe applicant company under the Registered Trade Mark “Skyphone”. Thisuses onboard terminals connected, through a satellite link between theaircraft and a satellite ground station, to the telephone network.Another system, TFTS (terrestrial flight telephony system, marketed as“Jetphone”), operates in a similar manner, but uses a direct linkbetween the aircraft and the ground station, without a satellite link.Similar systems are provided on board ships. However payment for theseservices is generally at the point of use (or prepaid), and may be in aforeign currency. Calls made to the user's cellular telephone will notbe successful unless the calls can be diverted to the telephone numberof the onboard user terminal (which will generally not be known to thecaller), and any special facilities offered by the user's cellularnetwork will in general be unavailable. A user with his own cellulartelephone account which, through “roaming” agreements between networkoperators, can be used in many different countries, would thereforeprefer to continue to use his cellular telephone subscription whentravelling within or between these countries on board an aircraft orother vehicle.

According to a first aspect of the invention there is provided apparatusfor enabling a first termination point of a first telecommunicationssystem to initiate call diversion instructions in the switching systemof a second telecommunications system such that calls initially directedto a telephone apparatus usable with the second telecommunicationssystem are diverted to a selected termination point in the firsttelecommunications system, the apparatus comprising means in the firsttelecommunications system for identifying the telephone apparatus fromwhich calls are to be diverted and the selected termination point towhich calls are to be diverted, and an interface means between the firsttelecommunications system and the switching system of the secondtelecommunications system, the interface means comprising:

means to indicate to the switching system that the telephone apparatusis in a specified operating condition, irrespective of the trueoperating condition of the telephone apparatus,

and means to generate an instruction to the switching system to divertcalls, intended for the telephone apparatus, to the said selectedtermination point of the first telecommunications system when thetelephone apparatus is indicated as being in the said predeterminedoperating condition.

A second aspect of the invention provides a first telecommunicationssystem, arranged for interconnection with a second telecommunicationssystem to allow calls initially directed to a telephone apparatus usablewith the second telecommunications relating to the telephone apparatus,means for receiving associated identification information relating tothe selected termination point, means for transmitting theidentification information to a network interface unit, means forreceiving authentication data from the interface unit, and means forconnecting calls to or from the selected termination point in responseto said authentication data. In the preferred arrangement the first andsecond telecommunications systems are a satellite telephone system and acellular telephone system respectively, the identification informationbeing a user identity associated with the telephone apparatus, and thenetwork address of the selected termination point.

A third aspect provides a network interface unit for interconnecting afirst telecommunications system with a second telecommunications systemsuch that calls directed to telephone apparatus configured for use withthe second telecommunications system may be diverted to a selectedtermination point in the first telecommunications system, the interfaceunit comprising:

means for receiving data identifying a user and a first terminationpoint in the first network,

means to indicate to the switching system of the secondtelecommunication system that a telephone terminal associated with theuser is in a specified operating condition, irrespective of the trueoperating condition of the telephone terminal, and means to generate aninstruction to the switching system of the second telecommunicationssystem to divert calls directed to the telephone user to the saidselected termination point of the first telecommunications system whenthe telephone apparatus is indicated as being in the said predeterminedoperating condition.

The telecommunications termination points may, for example, be userterminals of a satellite telephone system. They may be provided withreading apparatus for reading an information carrier encoded with theuser's identity. Such apparatus is commonly used for telephone terminalsto which the public have access to allow calls to be charged to a user'scredit card account, or an account with the service provider, or todeduct value from a stored value on the card.

In those cellular systems where the user identity is carried on a datacarrier card transferable between telephone handsets, the readingapparatus may be arranged to read this carrier. In the “GSM” standardthese cards are known as “Subscriber Identity Modules” or SIMs, and areeither of standard credit card size (86 mm×54 mm) or rather smaller (14mm×25 mm), and may be transferred from one cellular telephone handset toanother to allow the same telephone user account and directory number tobe used with different handsets.

Another embodiment allows the onboard user terminal to co-operate withthe complete cellular telephone. Although this requires a more complexinterface between the cellular telephone and the user terminal, itallows the user to use the functionality of his own telephone, ratherthan having to familiarise himself with that of an unfamiliar satelliteuser terminal.

However, as standard on-board satellite telephone card readers may notbe compatible with GSM “SIMs”, or complete telephones, the useridentity, or a code allowing its retrieval, may be carried on a specialcarrier compatible with the card reader to be used, and supplied tousers wishing to make use of the facility.

In a further variant, falling within the scope of the invention, theuser may gain authorisation for use of the system by entering apredetermined identification code using the user terminal, fortransmission to the interface unit which then retrieves the useridentity and establishes the diversion process as already discussed.

In the cellular telephone system of the preferred embodiment theinterface unit is arranged to appear to the switching system as if it isa typical radio base station control system, to which the mobile handsetis currently working, although in fact no radio base stations areactually controlled by it. This will be referred to as a “Virtual” BaseSite Controller. The switching system itself requires no modification:it merely registers that the user is working to the “Virtual” Base SiteController and stores the user details in its “Visitor LocationRegister” (VLR) as it would for a mobile unit working to any real basesite controller to which it is connected. The interface unit alsogenerates a call diversion instruction, which will appear to theswitching system to have come from the mobile handset, by way of the“Virtual” Base Site Controller. This call diversion instruction is setup in the switching system such that if the “Virtual” Base SiteController responds to a call request directed to the mobile unit with a“busy line” response (or some other specified condition), calls are tobe diverted, through normal network interconnects, to a specifieddirectory number, namely that of the satellite termination point towhich the user is connected. The interface unit does not in fact monitorthe real condition of the user terminal, (which is switched off oroperatively connected to the satellite network termination point by anon-radio link), but instead always returns the “line busy” signal tothe switching system.

Preferably, the interface includes a store to record any diversionsettings existing for the telephone apparatus prior to the diversion tothe second network being set up. This allows these settings to beretrieved when the user disconnects from the first telecommunicationssystem, so that they can be reinstated in the switching system of thesecond telecommunications system or transferred to a furthertelecommunications system if the telephone apparatus makes contact witha real radio base station, thereby initiating a handover procedure fromthe “Virtual” Base Site Controller to the real one.

Should a second call attempt be made, the switching system may bearranged to divert it to a predetermined number such as the user's voicemail. The interface unit may be arranged to transmit a message to thetermination point to indicate that such a voice mail message has beensent.

Some cellular telephones also have additional capabilities, such as forreceiving facsimile messages, or for connection by way of a modem to acomputer. A mobile user may have several network identities, all linkedto the same SIM, for controlling different cellular termination deviceshaving different capabilities. The standard at-seat satellite telephoneterminal provided in aircraft is not equipped to receive such calls.However, the vehicle on which the terminal is fitted may be providedwith a suitable terminal. Accordingly, the selected termination point towhich calls are directed may be a termination point other than the firsttermination point from which the process was initiated. Where such isthe case, the interface unit may be arranged to transmit a message tothe first termination point to indicate that such a message has beensent to the selected termination point.

If the user termination is in an aircraft or other vehicle connected toa ground station (by satellite or otherwise), it may move from the areacovered by one satellite (or ground station) to that of another. In thatcase, the network address of the termination changes. To accommodatethis, the interface may be provided with means to store the address oftermination points in the first system, means to record changes to thesaid addresses transmitted to it from the first system, and means tomodify the diversion instruction in the switching system when such achange takes place. Alternatively, the termination points may bearranged simply to repeat the set-up process, causing the mobile unit tobe re-registered with the interface unit, (which will not be apparent tothe switching system, as it will perceive the same “virtual” base sitecontroller), and to transmit a new call divert instruction to therevised address of the termination point.

The invention also provides a method of initiating, from a firsttermination point of a first telecommunications system, call diversioninstructions in the switching system of a second telecommunicationssystem such that calls initially directed to a telephone apparatususable with the second telecommunications system are diverted to aselected termination point in the first telecommunications system, themethod comprising the steps of;

in the first telecommunications system, identifying the telephoneapparatus from which calls are to be diverted and the selectedtermination point to which calls are to be diverted,

indicating to the switching system of the second telecommunicationssystem that the telephone apparatus is in a specified operatingcondition, irrespective of the true operating condition of the telephoneapparatus,

and generating an instruction to the switching system to divert calls,intended for the telephone apparatus, to the said selected terminationpoint of the first telecommunications system when the telephoneapparatus is indicated as being in the said predetermined operatingcondition.

This aspect of the invention comprises several separate processes, someof which comprise further aspects of the invention. These processesinteract to allow calls made to the telephone apparatus to be routed tothe selected termination point.

The first part of the process is carried out, in the describedembodiments, by a card reading device or similar apparatus associatedwith an onboard telephone termination point, which reads an informationcarrier encoded with the user's identity. The information carrier may bethe part of a cellular telephone containing the user identity.

The second part of the process is a method according to a further aspectof the invention, for interconnecting a first telecommunications systemwith a second telecommunications system to allow calls initiallydirected to a telephone apparatus usable with the secondtelecommunications system to be diverted to a selected termination pointin the first telecommunications system, comprising the steps of;

receiving, from a first termination point, identification informationrelating to the telephone apparatus,

receiving associated identification information from the firsttermination point,

transmitting the identification information to the second network,

receiving authentication data from the second network, and

connecting calls to or from the selected termination point in responseto said authentication data.

This process is, in the described embodiments, carried out by theground-based systems of the satellite telephone network.

The third part of the process is a method according to a further aspectof the invention, for interconnecting a first telecommunications systemwith a second telecommunications system such that calls directed totelephone apparatus configured for use with the secondtelecommunications system may be diverted to a selected terminationpoint in the first telecommunications system, comprising the steps of:

generating an instruction to the switching system of the secondtelecommunications system to divert calls directed to the telephoneapparatus to the said selected termination point of the firsttelecommunications system when the telephone apparatus is indicated asbeing in the said predetermined operating condition

receiving data identifying a user and a termination point in the firstnetwork,

indicating to the switching system of the second telecommunicationsystem that a telephone terminal associated with the user is in aspecified operating condition, irrespective of the true operatingcondition of the telephone terminal, generating an instruction to theswitching system of the second telecommunications system to divert callsdirected to the telephone user to the said selected termination point ofthe first telecommunications system when the telephone apparatus isindicated as being in the said predetermined operating condition.

This process is preferably carried out by an interface unit emulating abase site controller of the cellular network.

However, standard on-board satellite telephone card readers may not becompatible with GSM “SIMs”, or complete telephones. To avoid the need tomodify the user terminals, a user identity may be carried on a specialcarrier compatible with the existing card readers. This user identitymay be the user's cellular radio network identity (IMSI), or some otheridentity from which it can be derived.

In practice, the user identity required by the network (known in the GSMstandard as the IMSI) is unique to one carrier (the “SIM”) and is notencoded on any other. This provision is primarily a fraud preventionmeasure, made to prevent the user identity being used to access acellular network when the authorised user is actually elsewhere. Theinvention also requires access to a cellular network when the user isactually not directly connected to that network but is elsewhere, but iscommunicating through the first telecommunications system. It istherefore necessary for the interface means (“Virtual” Base SiteController) to obtain the user identity.

Embodiments of the invention will now be described with reference to theFigures, in which:

FIG. 1 is a schematic diagram showing the functional relationshipsbetween the systems which co-operate to form one embodiment of theinvention

FIG. 2 is a more detailed schematic diagram of the network terminationand associated card reading equipment, which for illustrative purposeswill be assumed to be on board an aircraft

FIG. 3 is a diagram showing part of an alternative arrangement ofnetwork termination, arranged for co-operation with a cellular telephonehandset

FIG. 4 is a schematic diagram showing the functional relationshipsbetween the components of the fixed part of the first telecommunicationssystem which co-operate in the invention,

FIG. 5 is a schematic diagram of the switching system, interface unit,and associated parts of the second telecommunications system;

FIG. 6 is a flow chart showing the process by which a diversion is setup in the second network to a termination connected to the first network

FIG. 7 is a flow chart showing the process by which a call coming in tothe second network is connected to a telephone connected to the firstnetwork

FIG. 8 is a flow chart showing the process by which the second networkrestores the original settings for a telephone when it disconnects fromthe first network.

FIG. 9 illustrates the forwarding process implemented to a data message.

FIG. 10 illustrates a conditional forwarding process for a data message.

FIG. 11 is a flow chart showing a call diversion process, for use whenthe system has to be temporarily shut down.

The following embodiments illustrate the invention using a standardswitched cellular network. However, the invention is applicable to othercellular networks, such as packet networks used to carry data over adistributed computer network such as the “Internet”, carrying messagesusing formats such as the “Internet Protocol” (IP). Thus, unless thecontext clearly demands otherwise, any reference in this specificationto switching includes the equivalent routing functions in a packetnetwork of this kind.

FIG. 1 shows the general arrangement of the various components whichco-operate in this embodiment. Note that traffic links (which can carryspeech, data, etc) are shown as full lines, signalling links used onlyfor call set up are shown as broken lines.

The onboard part 2 (shown in more detail in FIG. 2) comprises one ormore handsets 25 (which, in the alternative arrangement of FIG. 3, arethe users' own cellular telephone handsets 31), connected to atermination point 20 of the satellite network. The termination point 20is in communication with a ground station 4, shown in more detail inFIG. 4. In this embodiment, the communication link is made through anearth-orbiting satellite 6.

The principal components of the ground station 4 relevant to thisinvention are an antenna 44 which communicates, by way of the satellite6, with the onboard system 2, an Access Control and Signalling Equipment(ACSE) 40 which carries out call switching functions to allow calls tobe placed through the public switched telephone network (PSTN) 8 toother telephones 85, and a Card Management System 42 which authorisesthe use of an individual terminal 25 according to user identitiesentered with respect to that terminal. There is also a register 43 ofcard identities, to provide a correspondence between the user identitiesused by the satellite terminal and the corresponding cellular telephoneuser identities (not necessary if the cellular telephone identity isread directly by the terminal 20, as will be described with reference toFIG. 3), and to provide billing information.

The card management system 42 interacts with an interface unit 52 of a“host” cellular telephone network 5, shown in more detail in FIG. 5.This network 5 is connected to the public switched telephone network(PSTN) 8 and to other cellular networks 7 through a switching centre 50.Associated with the interface unit 52 there is an “aircraft locationregister” 41 which monitors the terminals currently served by eachindividual satellite, and modifies the functioning of the interface unit52 when a terminal 20, for example on board an aircraft 2, moves fromthe coverage area of one satellite 6 (and its ground station 44) toanother.

The cellular network 7 illustrates in simplified form the systemarchitecture of a “GSM”-standard cellular radio system, and theterminology used in this standard. The network 7 has a switching system(MSC) 70 to allow connection of one or more base transceiver sites (BTS)74, through one or more base site control systems 72, to the PSTN 8 andthus to other telephones 85. A mobile telephone 75 may establish radiocontact with one of the base stations 74 in order to make and receivetelephone calls. The network 7 also includes a “Visitor LocationRegister” 71, which maintains details of those cellular telephones 75currently co-operating with the network 7. Mobile telephones accordingto the “GSM” standard are capable of co-operating with differentnetworks (“roaming” between networks). To allow this to take place, whena mobile telephone 75 changes from one network to another, the networkto which it has moved retrieves data from a “Home Location Register” 73permanently associated with the handset 75. The network 7 in which theHome Location Register 73 associated with a given handset is to be foundis identifiable from the handset's identity code. The Home LocationRegister also records the identity of the network 7 with which themobile handset 75 is currently operating.

The “host” network 5 operates like conventional cellular network, but isprovided with an interface unit 52, which interacts with the mobileswitching centre 50 as a base site controller would. This interface unit52 may be in addition to one or more base site controllers (not shown).The interface unit does not interact with any base transceiver sites ormobile handsets, but obtains user details (in particular the identity ofa mobile handset) from the card management system 42 to allow it toappear to the switching centre 50, and the HLR 73 in the user's homenetwork, that it is in radio communication with a mobile handset 25. Itcan then control the call forwarding instructions stored in the hostnetwork VLR 51, to cause incoming calls directed to that handset to bediverted, through the switching system 40 of the satellite network 4, tothe satellite terminal 20.

FIGS. 2, 3 and 4 illustrate embodiments of the invention, applied to asatellite telephone system such as that provided by the applicantcompany under the Registered Trade Mark “Skyphone”. FIG. 2 shows a firstembodiment of the mobile part which has a standard card reader, whilstFIG. 3 shows an alternative arrangement which allows a user to use hiscellular telephone handset. FIG. 4 shows the ground station.

The onboard system 20 shown in FIG. 2 comprises a plurality of userterminals 21, 21 a (only one shown in detail), connected by a multiplexand radio interface unit 28 to an antenna 29 which provides radiocommunication with a satellite 6 or a ground station. Each user terminal21 has a card reading unit 23 into which an intending user can insert acard 24 or other data carrier providing user identification data. Thedata may give details of the user's credit card account, or a specialaccount for the use of the onboard telephone service. The card reader 23may be adapted to read the SIM (Subscriber Identity Module) of aGSM-standard cellular telephone. (It should be noted that one variant ofthe method according to the invention does not make use of the cardreading apparatus 23,24,26, although this apparatus may nevertheless bepresent for use by other customers of the satellite system).

Further user terminals 21 a may be set aside for non-voice applications,for example an onboard facsimile machine.

The user handset 25 provides the usual keypad, microphone and earphoneto allow the user to make telephone calls. The user handset 25 and thecard reader 23 are both connected to a processor 26 which converts dataread from the card 24, and keystrokes input from the handset 25, intodata signals for transmission over the radio link 29. It also providesidentification data indicative of which of the terminals 21 it is. Afurther processor 27 performs analogue/digital conversion of speechsignals from the handset 25.

The digitised signals from each terminal 21 are multiplexed andmodulated onto a radio carrier in the interface unit 28, and transmittedfrom the antenna 29.

The antenna 29 also receives signals which are demodulated anddemultiplexed in the interface 28. Data signals are processed in theprocessor 26, whilst digitised speech is converted to analogue speech inthe analogue/digital converter 27 and fed to the handset 25.

The interface unit 28 also includes a connection to the data bus 22 ofthe aircraft 2 giving access to aircraft parameters such asundercarriage deployment, “weight-on-wheels”, time to destination,altitude, etc. When a predetermined condition indicative of theimpending end of a flight is met, the central unit 28 transmits a signalto the ground station to cause a deregistration signal to be transmittedto the card management system 42.

Because the onboard telephone system was originally designed for makingoutgoing calls, the handsets 25 provided in existing terminals 21 arenot equipped with a suitable call alerting device. The handsets 25 couldbe modified to provide a buzzer or light to alert the user to anincoming call. Alternatively, to avoid distracting other passengers onthe aircraft, the telephone terminal 21 may be connected to an at-seatentertainment system 200, to provide an alert either through theearpieces 202 or on the screen 201.

Instead of the terminals 25, an alternative arrangement may be used asshown in FIG. 3. In this arrangement each onboard terminal 25 isreplaced by an onboard interface device 311 to which a user's own mobileradio telephone 31 can be connected electrically, thereby allowing themobile telephone to be used without using its radio antenna. It is amodification of the system described in the applicant company'sInternational Patent Application WO97/36442, published on 2^(nd) Oct.1997, to which the reader is referred for further details. In thismodified version a GSM (Global System for Mobile communication) mobiletelephone 31 comprises r.f. transceiver circuitry 32 coupled to anantenna 33, base band signal processing and control circuitry 34, arechargeable battery pack 35, a switch 36 and a socket 37. Theprocessing and control circuitry 34 has a data output terminal 34 acoupled to both the r.f. transceiver circuitry 32 and a first contact 37a of the socket 37. A data input terminal 34 b of the processing andcontrol circuitry 34 is coupled to the r.f. circuitry 32 and a secondcontact 37 b of the socket 37. A third contact 37 c of the socket 37 iscoupled to a control input of the processing and control circuitry 34.

Fourth and fifth contacts 37 d, 37 e of the socket 37, which arerespectively for 0 V and +V power supply lines, power the telephone 31,and may also be arranged to recharge its batteries 35. The +V terminalof the battery pack 35 is also connected to the processing and controlcircuitry 34 and to an input terminal of the switch 36. The outputterminal of the switch 36 is coupled to a +V input terminal of the r.f.circuitry 32. A control terminal of the switch 36 is coupled to anoutput of the processing and control circuitry 34.

The interface unit 311 comprises a control circuit 312, a user inputunit 313, including a keypad and a display, a V.24 33.6 kbit/s modem314, a power supply unit 315 and a plug 316. The plug 316 has fivecontacts 316 a–316 e which correspond to contacts 37 a–7 e of the socket37 of the mobile telephone 31. The first contact 316 a of the plug 316is coupled to a data input terminal of the control circuit 312 and thesecond contact 316 b of the plug 316 is coupled to a data outputterminal of the control circuit 312. A bi-directional serial link 318 isprovided between the control circuit 312 and the modem 314 for modemcontrol and data signals. The third contact 316 c and fifth contact 316e of the plug 316 are coupled to the +V output of the power supply unit315. The fourth contact 316 d of the plug 316 is coupled to theinterface unit's 0 V supply wiring. The user input unit 313 is coupledto the control circuit 312 for the input of user commands and the outputof display control signals from the control unit 312 to the user inputunit 313. The +V output of the power supply unit 315 is also coupled to+V input terminals 312 a, 313 a, 314 a of the control circuit 312, theuser input unit 313 and the modem 314. The modem 314 is coupled to atelephone line 317 and the power supply unit 315 is arranged to receivepower from an electricity supply 319.

When the user wishes to connect to the interface unit 311, he connectsthe plug 316 of the interface unit 311 to the socket 37 on his telephone31 by a cable (not shown). The voltage on the third contact 37 c of thesocket 37 is detected by the processing and control circuitry 34 whichthereby determines that the telephone 31 has been connected to theinterface unit 311. The connection of the battery 35 to the power supply315 by way of the connections 37 d/316 d and 37 e/316 e also allows thebattery to be recharged.

Once the processing and control circuitry 34 has determined that thetelephone 31 has been connected to the interface unit 311, it sends acontrol signal to the switch 36, causing it to open, isolating the r.f.circuitry 32 from the battery pack 35 and the power supply 315 in theinterface unit 311. The processing and control circuitry 34 alsoresponds to the voltage on the third contact 37 c of the socket 37 byselecting alternative control programs or constant data to allow fordelays in the signal path from the telephone 31 to the controller 30which are caused by the use of the satellite link 6 and the modems 314,32.

In this arrangement, instead of the need for a separate card reader 23,the telephone 31 identifies itself to the telephone network 40/42 bygenerating its terminal identity code (IMSI in the case of a GSMtelephone). The registration signal is not transmitted from the antenna3 because the r.f. circuitry 32 is disabled. Instead, it is output tothe interface unit 311 via the first contacts 37 a, 316 a of the socket37 and plug 316.

The operation of this onboard system will now be described withreference to FIG. 6. When the card reader 23 or interface unit 311detects the presence of a card 24 or handset 31 respectively, (step 601)it generates a prompt to indicate to the user that he may wish to havecalls diverted to the onboard system. If the user requires this service,he enters a code on the keypad of the handset 25, 31 which causes adivert request to be generated (step 602). The details from the card 23(or SIM of the handset 31) are then passed to the processor 26 whichalso provides the identity of the terminal 21 (step 603) and transmitsthe data to the interface unit 28.

Alternatively, these steps (602, 603) may be activated by the userwithout a card, by dialling an access code (divert request 602) followedby further keystrokes to identify the account to be used (terminalidentity step 603). These keystrokes may include the user's MSISDN(which, as his own directory number would be known to him). To preventmisuse of the system by unauthorised personnel, a security code(Personal Identification Number: “PIN”) may be added. This code may havebeen issued previously to the user, or the user may request such a codeby making a call using the satellite system to his home network'scustomer service department and providing personal details to theoperator to prove his identity.

The user may select for the identity of a terminal 21 a other than hisown at seat terminal 21 to be selected as the destination for incomingcalls. For example, if his MSISDN code (or one of them) relates to afacsimile machine having cellular capability, he may request thatincoming calls to that number be directed to an onboard facsimilemachine 21 a.

The data received by the central unit 28 is then transmitted to theground station 4 (step 604). The further steps (605–615) in the processare carried out by the co-operating networks 4, 5 and will be describedlater.

If the user decides that he no longer wishes to have his calls divertedto the terminal 21, he may cancel the diversion instruction by enteringa special code on the keypad of the handset 25, 31. Disconnect codes mayalso be generated in the central unit 28 for all the termination points21, either by the cabin crew or automatically in response to a signaldetected on the aircraft's data bus 22 which is indicative of theimminent end of the journey, such as undercarriage deployment, weight onwheels, low altitude, or time remaining to destination as determined bythe aircraft's flight management system. The disconnect instruction istransmitted (step 801, FIG. 8) by way of the switching system 40 in theground station 4, to the interface unit 52 whose operation (steps 802 to805) will be described later.

The Ground Station 4 shown in FIG. 4 has a radio antenna system 44 forcommunicating with the terminal 20, through a satellite link 6 orotherwise. Signals are handled by an Access Control Signalling Equipment(ACSE) 40 which carries out switching functions to route calls to orfrom the public switched telephone network (PSTN) 8.

A card management system 42 comprises a data acquisition unit 47 whichreads data transmitted from the card reader 24, and/or keyed in by theuser, to identify the type of user, confirm the user's account detailsand arrange billing for any calls made, through a billing system 45which raises invoices, or interacts with the systems of a credit cardoperator or bank.

In the existing onboard systems a user cannot receive calls, unless thecaller knows the unique “AES” number of the handset 21, 21 a. This isunlikely, as the number depends on the identity of the aircraft, theseat, and the serving satellite or base station.

The conventional ground station equipment just described is augmented inthe present embodiment by an interface 46 with the Home LocationRegister 73 of each network 7 whose subscribers are to be given accessto the service. The interface 46 which stores a concordance between thecard identities and the card-holder's cellular radio telephone number(MSISDN: mobile systems integrated services data network number), onrequest from the data acquisition unit 42, which is arranged torecognise the card identities which require such translation. In apreferred embodiment the concordance is supplied to a register 43 in theground station by the operator of user's home network 7, when thenetwork operator provides the user with the card. The operator of thehome network 7 also records the concordance in its own Home LocationRegister 73. This arrangement allows the existing card readers 23 to beused on board the aircraft, without modification. If the users' mobilesubscriber identities are supplied from the onboard system, either byreading the identity (reader 311) or by the user keying it in, the store43 can be used for verification, or omitted. Billing information is alsoreturned to the user's home network 7.

The operation of the ground station will now be described with referenceto FIG. 6. The data acquisition unit 47 receives the card details fromthe reader 23 (see steps 601 to 604 already discussed) and if itidentifies as those details as corresponding to a cellular user (step605), it retrieves the cellular user identity from the store 43containing this concordance, or from the HLR 73 of the user's homenetwork, (step 606). (This step can be omitted if the user's mobilenetwork identity is provided by the onboard apparatus 20).

The data transmission unit 46 then generates a signal for transmissionof the cellular user identity, together with the identity of theterminal 21, to the cellular network 5 acting as host to the interface(step 607). This host network 5 will, in general, not be the same as theuser's home network 7. The further steps (608 to 615) in this processwill be described later, with reference to FIG. 5.

If a cancellation signal is received from the aircraft in respect of agiven terminal 21, (step 801, previously discussed) the datatransmission unit 46 transmits a “cancellation” signal to the hostnetwork 5. As already discussed, the cancellation signal may begenerated either for an individual handset 21, by its user dialling aspecial code, or for all handsets as the result signals received by theradio interface unit 28 over the aircraft's data bus 22 indicative ofthe imminent end of the flight.

An embodiment of the host network 5 of the invention is shown in FIG. 5.Its operation will be discussed with reference to FIGS. 6, 7 and 8. Inthis network 5 an interface unit 52 is provided, which is arranged toappear to the switching system 50 as if it is a normal base station ofthe cellular radio system.

In order to do this, the interface unit 52 is provided with a dataacquisition unit 54 which receives from the card management system 42 ofthe ground station 4 the identity of the cellular telephone it is torepresent, and the AES identity of the onboard terminal 20 (step 608,FIG. 6). Mobile telephones have three identification codes: theequipment identity (IMEI, which will not be discussed further here), thedirectory number (MSISDN) and the actual SIM identity (IMSI). Inpractice, for security reasons, the IMSI is not made generally known,and a user is normally identified by his MSISDN unless the SIM itself isused. If the SIM is used in the card reader 23, or the user's telephoneis used in the arrangement of FIG. 3, (in which case no concordance isrequired) the IMSI can be read directly from the data received by thedata acquisition unit 54. However, if the user keys in his ownidentification data (step 603), or a concordance is provided by the cardreader 23, the data acquisition unit will receive the MSISDN, and notthe IMSI. (There may also be a PIN or other security code, which ischecked by the data acquisition unit 54).

In the GSM standard it is possible to obtain an IMSI if the MSISDN isknown by interrogating the appropriate Home Location Register 73. To dothis, the interface unit 52 transmits a “request for routinginformation” signal, using the MSISDN (step 609). The standard HLR 73responds to such a request with a signal which includes the IMSIcorresponding to the MSISDN in the request (step 610). (This “requestfor routing information” signal was provided under the GSM standard as ameans of obtaining routing information for data messages intended for adestination for which only the MSISDN number is known. However, it maybe used for other purposes, such as that described above).

The telephone identity (IMSI), whether obtained directly from the cardreader 23 or handset 31, or indirectly as just described, is passed to anetwork registration unit 55 which exchanges signals with the mobileswitching centre 50 in the same way that a real cellular telephone woulddo. The mobile switching centre therefore informs the user's HomeLocation Register 73 that the mobile telephone is now registered withthe network 5 (step 611). The Home Location Register 73 records that themobile handset is now registered with host MSC 50 (step 612).

It should be noted that, although registered with the host MSC 50, theuser's mobile handset is not operatively connected to the host MSC 50—infact the mobile handset may be switched off to allow the card 24 to beused, or it may be connected to a user terminal 311. The user may be inan aircraft, anywhere in the world within the coverage area of thesatellite network.

The user's details, including any diversion instructions, are sent bythe Home Location Register 73 to the network's VLR 51 (step 613). Astore 57 records a copy of the details of these diversion instructions(step 614).

Conventionally, any incoming calls for a mobile user are sent in thefirst instance to the user's home network 7, and the HLR 73 providesinformation to identify the MSC 50 where the mobile handset cancurrently be found. Consequently, in the present arrangement, anyincoming calls intended for the mobile user will now be directed to thenetwork 5, as the mobile user is currently registered there.

The data acquisition unit 54 in the interface 52 now passes thedirectory number of the termination point 21 to a call diversioninstruction unit 56, which generates a “divert on busy” instruction tothe VLR 51 (step 615). This is a standard divert arrangement, andoperates such that should the mobile unit appear to be engaged onanother call when a call attempt is made to it, the call attempt isdiverted to a specified directory number, in this case the terminationpoint 21 or 21 a, (identified by its AES code). This diversioninstruction replaces any previous instruction held in the VLR 51.Further settings may be made in the call diversion instruction unit 56,such as the identification of a termination point 21 to which a datamessage is to be sent when a call is diverted to another terminationpoint 21 a.

Of course, there is in fact no mobile telephone connected to theinterface unit 52, and therefore it is unable to connect incoming callsto the mobile telephone in the conventional way, or to identify thecurrent true operating condition (switched off, busy, ready for calls,etc) of the mobile handset. Instead, the system responds to a callattempt as will now be described with reference to FIG. 7.

When a call attempt is made (step 701), the home MSC to which the callis initially routed obtains from the HLR 73 the current location of themobile telephone (step 702), and on receiving the identity of the hostMSC 50 (step 703), directs the call there (step 703). The host MSC 50 inturn transmits the call attempt to the currently serving base station,which is in fact the interface unit 52 (step 704). If the disconnectprocedure (to be described later with reference to FIG. 8) has beencarried out, the call will not be connected to the onboard system (step705), and instead a signal is transmitted back to the home MSC 70.Otherwise, call attempts received by the interface unit 52 are handledby a call request handling unit 58, which automatically returns a “busy”signal to any such request (step 706). The MSC 50, on receiving the“busy” signal, retrieves the diversion information from the VLR 51 (step708) allowing it to route the call through the PSTN 8 to the userterminal 21, 21 a (step 710).

In the event that the destination terminal 21 a is not the terminal 21that originated the instruction, the call request handling unit 58 ofthe ground-based interface unit 52 may be arranged such that whenever amessage addressed to the user's MSISDN is diverted to the terminal 21 a,the call request handling unit 58 also generates a data message (step711) for transmission to the instructing terminal 21 by way of the MSC50, PSTN 8, and satellite system 4, 6 (step 712) either during the callor after it ends. Such a message can be used for example to alert theuser of the terminal 21 that a facsimile message addressed to him hasbeen sent to the terminal 21 a. As with the call alerting processdescribed above, the message may be displayed using the in flightentertainment system 200.

If a second call attempt is made, the ACSE 40 may identify that thedivert instruction will not work as it is currently handling a divertedcall to that number. The default condition in such cases is to arrangefor the second call to be diverted to the user's voicemail address (notshown) in his home network 7. The user may also be sent a data messageto inform him of the new voicemail message. This message would normallybe sent to the mobile unit, which appears to the MSC 50 to beco-operating with the interface unit 52, so the MSC 50 transmits thedata message to the interface unit 52 (step 711). In order to inform theuser of the new voice mail message, the interface unit 52 nowregenerates the data message for forwarding to the user terminal 21 viathe MSC 50, PSTN 8, and satellite system 4, 6 (step 712) either duringthe call or after it ends.

In order to inform the user of the new voice mail message, the interfaceunit 52 must now forward the data message to the user terminal 21 (step712) either during the call or after it ends. However, data messages arenot suitable for switching via the MSC 50 and PSTN 8, nor for handlingby the on-board terminal 21 as it is only equipped for voice. Becausethe IMSI is recorded in the HLR 73 as being registered with the“Virtual” BSC, or interface unit, 52, any other data messages intendedfor the user will also be routed to the interface unit 52, and requireforwarding to the user. As with the call alerting process describedabove, the message may be displayed using the in flight entertainmentsystem 200.

To allow the use of the at seat display system 201 for data messages,not suitable for transmission over the PSTN and satellite system intheir original form the interface unit 52 is provided with a datahandling processor 53 for receiving data messages received over a packetdata system 9 by way of the MSC 50 and intended for users currentlyassociated with the interface unit 52. These messages include SMSmessages sent from other callers, and SMS messages generated by the MSC50 itself to alert the user that a message has been sent to the voicemail system. The format of such a message is shown in FIG. 9, and theprocess of sending and receiving it is shown in FIG. 10.

The original message 900 basically consists of a data payload 901 and anaddress 902, which is the IMSI of the destination mobile telephone (FIG.9 a).

When the interface unit 53 receives such a data message (step 990) itretrieves from the data acquisition unit 54 the data network address ofthe at-seat entertainment terminal 200 corresponding to the user'scellular identity which was originally provided to the data acquisitionunit 54 when the user carried out the registration procedure (step 991).The interface unit 53 next generates a data call to that address (step992), in a form suitable for transmission by the MSC 50 (step 993) overthe packet data network 9 to the aircraft 2, with an address headercorresponding to the data network address of the user's at-seat terminal200. This data call may be a short message to indicate that a message isawaiting delivery, and displaying on the screen 201 an invitation to theuser to dial a special code on his handset 25 to accept the message(step 994), and any charge associated with it. This acceptance istransmitted back, by way of the MSC 50 to the interface unit 53 (step995). (These steps 992–995 may be omitted if it is not required forusers to acknowledge acceptance before receiving a data message).

The interface unit 53 then replaces the address header (the IMSI) 902 inthe original data message with a code 912 identifying the terminal 200and encapsulates the message in a form suitable for transmission overthe packet data network 9 to the aircraft (step 996), with an addressheader 910 to send it to the data network interface server 28 servingthe onboard entertainment system 200. It can thus be transmitted to thedata interface 28 over the packet data network 9 (step 997), effectivelyas a packet with an address header 910 and a payload made up of theat-seat terminal number 912 and true payload 901 (FIG. 9 b).

On receipt of the data message, the data interface 28 extracts the datamessage payload 901, 912, (FIG. 9 c) (step998) and identifies theindividual at-seat terminal 200 identified by the address 912. It canthen cause display of the data message payload 901 on the screen 201 ofthe appropriate terminal (step 999).

If password protection is required, for example to ensure that the useris present when the message is displayed, the payload 901, 912 can alsoinclude a password code 913, which causes the interface server 28 towithhold the remainder of the payload until a predetermined sequence ofkeystrokes has been entered by the user in the terminal 200.

As the termination is itself mobile, being on board an aircraft, callrouting to that termination may require revision from time to time. Forexample, the “Inmarsat” satellite system comprises several geostationarysatellites, which each provide cover for part of the earth's surface.These areas of coverage overlap to a large extent, but nevertheless on along flight the aircraft may pass out of the area covered by onesatellite into that served by another. This causes a small butsignificant change in the network address of any satellite terminal onboard the aircraft. The aircraft location register 41 monitors theidentity of all aircraft currently being handled by each ground station4. When an aircraft location is updated, the call diversion instructionunit 56 responds by transmitting a new call diversion instruction to theVLR 51 so that any further incoming call attempts are diverted to thenew network address of the terminal. Note that the diversion store 57 isnot updated. Note also that this does not affect calls already inprogress: there is usually sufficient overlap in coverage areas thathandover from one satellite or base station to another can be arrangedto take place when no call is in progress.

FIG. 11 shows a process for intercepting calls when the onboard system 1is switched off at times when its operation could interfere withconventional land-based cellular systems or with electronic controlsystems of the vehicle, to enforce “quiet” periods on board, or to allowtransfer of the satellite link from one satellite to another. Thecontrol to switch the system off may be performed manually or under thecontrol of a sensor detecting interference from nearby radio basestations 74, or an operational condition of the vehicle, such asdeployment of the aircraft undercarriage, low altitude, or “weight onwheels”, communicated to the onboard system by means of a control databus e.g. 22. When such a disconnection occurs (step 1501), a signal isgenerated in the onboard system 2 (step 1502) for transmission over thesatellite link 6 to the ground station 4 (step 1503). This signal causesthe satellite ground station to invoke a call failure mode for any calldirected to the onboard system 2 of the specified vehicle (step 1504).

Any call now diverted by the MSC 50 to a number corresponding to a nodeon board the vehicle (step 1505) will then receive a “call failed”indication from the ground station (step 1506), without any signallingrequired over the satellite link 6. Such failed calls will be re-routedaccording to the user's own diversion instructions, stored by the hostMSC 50 for use when the user's handset is busy (step 1507). Generally,such instructions will be to divert the call to a voicemail system inthe user's home network. In addition, the host MSC 50 will record theexistence, and possibly the origin (Calling line identity—CLI) of anysuch call attempts (step 1508).

When the onboard system 2 is re-activated (step 1511) a further signalis transmitted by the onboard system (step 1512) for transmission overthe satellite link 6 to the ground station 4 (step 1513). This signalcauses the satellite ground station to revoke the call failure mode forcalls directed to the onboard system 2 of the specified vehicle (step1514). When a user 21 reconnects to the onboard system 2 (step 1515) theonboard system transmits a signal to the host MSC 50 (step 1516) whichcauses the host MSC 50 to retrieve the call attempt record previouslystored for that user (step 1518). If one or more such call attempts havebeen made, the MSC returns a message to the user terminal 21 (step1519), prompting the user to retrieve his messages from the voicemailsystem should he so wish.

Generally, the detection of the same IMSI from two sources would causethe HLR to disconnect both callers as a fraud prevention measure. Sincethe present system causes the generation of an IMSI from the interfaceunit 52, instead of directly from the mobile telephone to which thatIMSI relates, the user's mobile telephone should be switched off, orconnected to an onboard interface device 311 which disconnects the radiocircuits, to prevent the network detecting the IMSI in two places, whichwould disrupt the call routing processes in the HLR 73 and elsewhere. Ifthe user is on board an aircraft, he should not be using his mobilehandset in the conventional manner, and so there should be no problem.However, if the user, having left the aircraft, switches on histelephone 75 before the network 5 has reported a loss of the mobile unitfrom its own network, the mobile unit may be perceived by the HLR 73 asbeing registered with two networks at once. To avoid this possibility, adisconnection procedure is followed as described with reference to FIG.8.

As already discussed, a disconnection signal may be transmitted from theon board system 28 to the card management system 42 and thus to the hostnetwork's interface unit 52 (step 801). The disconnection signal may beactivated by a special code entered by the user 21, or it may begenerated automatically by data collected from the aircraft's data bus22, indicative of the imminent end of the flight. Note that thisdisconnection signal merely controls the interface 52—it has no effecton calls in progress, which is routed from the MSC 5 by way of the PSTN8.

The disconnect instruction is received by the interface unit 52 (step802) and causes the call diversion instruction unit 56 to retrieve thecall diversion data stored in the store 57 (step 803) and generate acall diversion instruction restoring the original settings to the VLR 51(step 804). This ensures no further calls are routed to the onboardterminal 21.

The interface unit 52 next causes the network registration unit 55 inthe interface unit 5 to instruct the MSC 50 that the user is no longerconnected to the network 5 (step 805). This allows the mobile unit toregister with another network 7 in the normal way. Call attempts to theuser number will continue to be routed by the Home HLR 73 to the MSC 50with which the mobile unit was most recently registered, but as the MSCcannot now find the mobile unit, any such incoming call will return a“not found” signal to the home MSC 70 which will divert the callaccording to any diversion instructions set up, or fail the call.Alternatively, the host MSC 50 may handle the diversion itself if themobile unit is “not found”, using the original diversion instructionsnow in the VLR 51, having been retrieved from the store 57 (step 804above).

Having left the aircraft, the user may switch on his mobile telephone75, which will register with the local network (e.g.7) and will retrievethe original divert information from the HLR 73 (note that in generalthe HLR 73 will not be in the same network), and will cause all datarelating to the user to be deleted from the VLR 51 in the “host” network5.

1. A method for forwarding incoming cellular communications to anaircraft, comprising: receiving a request to divert incoming calls for acellular telephone number to a communication system on board anaircraft; associating a divert on busy instruction with the cellulartelephone number, the divert on busy instruction representing aninstruction to forward an incoming call for the cellular telephonenumber to the communications system aboard the aircraft; and consideringa state of a cellular telephone associated with the cellular telephonenumber as busy, regardless of an actual state of the cellular telephone;wherein, an incoming telephone call to the cellular telephone number isforwarded, consistent with said considering and in accordance with thedivert on busy instruction, to the communications system on board theaircraft.
 2. The method of claim 1, wherein said associating a divert onbusy instruction comprises giving priority to an address of thecommunications system on board the aircraft over any previous divert onbusy instruction.
 3. The method of claim 1, wherein the communicationsystem on board the aircraft is a telephonic device aboard the aircraft.4. The method of claim 1, wherein the communication system on board theaircraft is a communication device electrically coupled with a cellulartelephone aboard the aircraft.
 5. The method of claim 1, wherein thecommunication system on board the aircraft is a facsimile machine. 6.The method of claim 3, wherein the telephonic device is an aircrafttelephone handset station.
 7. The method of claim 1, wherein saidassociating a divert on busy instruction comprises modifying a presetdivert on busy instruction associated with the cellular telephone toinclude the communication system on board the aircraft.
 8. The method ofclaim 1, further comprising: receiving an incoming call for the cellulartelephone number; and forwarding the incoming call to the communicationsystem on board the aircraft.
 9. The method of claim 1, the cellulartelephone having at least one original divert on busy instruction priorto said associating a divert on busy instruction, the method furthercomprising: receiving an incoming call for the cellular telephonenumber; diverting, in response to an actual state of the cellulartelephone being busy, the incoming call consistent with the at least oneoriginal divert on busy instruction.
 10. A method for routing incomingcellular telephone traffic through a land-based host network to acellular device user aboard an aircraft, the cellular device user havingan associated cellular telephone number, comprising: receiving, at thehost network, a request to register the presence of the cellular deviceuser aboard the aircraft; the host network advising the cellular deviceuser's home network that the cellular device user is within theoperating jurisdiction of the host network; associating, at the hostnetwork, a primary divert on busy instruction with the cellulartelephone number, the divert on busy instruction representing aninstruction to divert an incoming call to a communication system onboard the aircraft; and considering a current operational stateassociated with the cellular telephone number as busy, regardless of anactual operational state of the cellular device; wherein, upon receiptof an incoming call to the cellular telephone number, the host forwardsan incoming call to the communication system on board the aircraftconsistent with the primary divert on busy instruction.
 11. The methodof claim 10, wherein said associating a primary divert on busyinstruction comprises giving an identifier of the communication systemon board the aircraft priority over any preset divert on busyinstruction.
 12. The method of claim 10, wherein the communicationsystem on board the aircraft is a telephonic device aboard the aircraft.13. The method of claim 10, wherein the communication system on boardthe aircraft is a communication device electrically coupled with acellular telephone aboard the aircraft.
 14. The method of claim 10,wherein the communication system on board the aircraft is a facsimilemachine.
 15. The method of claim 12, wherein the telephonic device is anaircraft telephone handset station.
 16. The method of claim 10, whereinsaid associating the primary divert on busy instruction comprisesmodifying preset diversion instructions associated with the cellulartelephone to include the communication system on board the aircraft. 17.The method of claim 10, further comprising: receiving an incoming callfor the cellular telephone number; and forwarding the incoming call tothe communication system on board the aircraft.
 18. The method of claim10, the cellular telephone having at least one original divert on busyinstruction prior to said associating a primary divert on busyinstruction, the method further comprising: receiving an incoming callfor the cellular telephone number; and diverting, in response to anactual state of the cellular telephone being busy, the incoming callconsistent with the at least one original divert on busy instruction.19. A method of registering to divert a telephone call to atelecommunications device on-board a vehicle, the method comprising:receiving first and second identification information, the firstidentification information being associated with a cellular device, thesecond identification information being associated with thetelecommunications device; associating modified divert on busyinstructions with the cellular device that identify thetelecommunications device as a divert on busy instruction; and settingan indication of a status of the cellular device as busy regardless ofan actual status of the cellular device.
 20. The method of claim 19further comprising the steps of: receiving a telephonic call intendedfor the cellular device; diverting the telephonic call to the on-boardtelecommunications device consistent with the primary divert on busyinstruction.
 21. The method of claim 19 wherein the on-boardtelecommunications device includes a facsimile device.
 22. The method ofclaim 19, wherein said associating comprises inserting atelecommunications device identifier as a primary divert on busyinstruction within any existing divert on busy instructions.
 23. Themethod of claim 19, wherein said receiving, associating and settingoccur at a host network, the cellular device is associated with a homenetwork different from the host network, and said method furthercomprising advising the home network that the cellular device is roamingwithin the coverage of the host network.
 24. A method of registering todivert incoming cellular telephone calls to an on-boardtelecommunications device, the method comprising: registering a cellulardevice as roaming on a host network regardless of the actual location ofthe cellular device relative to the host network; and updating, inresponse to said registering, a primary divert-on-busy instruction ofthe cellular device as an on-board telecommunication device.
 25. Themethod of claim 24, further comprising setting an indication of a statusof the cellular device as busy regardless of an actual status of thecellular device.
 26. The method of claim 24, wherein the cellular deviceis associated with a home network, said method further comprisingadvising the home network that the cellular device is roaming on thehost network.
 27. The method of claim 24 further comprising the stepsof: receiving a telephonic call placed to the cellular device; anddiverting the telephonic call to the on-board telecommunications device.28. The method of claim 24 wherein the on-board telecommunicationsdevice includes a facsimile device.
 29. A method of receiving atelephonic call placed to a mobile station at a telecommunicationsdevice on-board a vehicle comprising: receiving a call forwarded from ahome network, the call being placed to the mobile station; returning abusy signal for the mobile station regardless of an actual state of themobile station; accessing a divert-on-busy instruction for the mobilestation; and forwarding the call to the vehicle consistent with saidaccessing; wherein the call terminates at the telecommunications deviceon-board the vehicle.
 30. The method of claim 29, wherein the on-boardtelecommunications device comprises a facsimile device.
 31. The methodof claim 29, further comprising setting an indication of a status of themobile station as busy regardless of an actual status of the cellulardevice.
 32. The method of claim 29, wherein the mobile station isassociated with the home network, said method further comprisingadvising the home network that the cellular device is roaming on a hostnetwork.
 33. A method of receiving a telephonic call placed to acellular device at a telecommunications device on-board a vehiclecomprising: receiving first and second identification information, thefirst identification information being associated with a cellulardevice, said second identification information being associated with thetelecommunications device; associating modified divert on busyinstructions with the cellular device that identifies thetelecommunications device as a divert on busy option; setting anindication of a status of the cellular device as busy regardless of anactual status of the cellular device; receiving a call forwarded from ahome network, the call being placed to the cellular device; accessingthe modified divert on busy instructions for the cellular device; andforwarding the call to the telecommunications device consistent withsaid accessing; wherein the call terminates at the telecommunicationsdevice on-board the vehicle.
 34. The method of claim 33, wherein theon-board telecommunications device includes a facsimile device.
 35. Themethod of claim 33, wherein the mobile station is associated with thehome network, said method further comprising advising the home networkthat the cellular device is roaming on a host network.
 36. The method ofclaim 33, wherein said associating comprises inserting atelecommunications device identifier as a primary divert on busyinstruction within any existing divert on busy instructions.
 37. Themethod of claim 33, said method further comprising routing, when saidactual status of the cellular device is busy, the call consistent withthe existing divert on busy instructions.